198 



PALEOZOIC TIME. 



Utica shale ; and another from the Hudson River heds at Guilderlaud, 

 near Albany, N. Y. 



The black Utica shale abounds in combustible material, although 

 containing no coal. Whitney found about 21 per cent, in the shale of 

 Savannah, 111. ; 11 to 16 per cent, in that of Dubuque; and 12 to 

 14 per cent, in that of Herkimer County, N. Y. 



The Trenton formation in East Tennessee affords a reddish varie- 

 gated marble of great beauty, and also a grayish-white variety, which 

 are extensively worked and exported. 



III. Life. 



1. Plants. 



Sea-weeds are the only known fossil plants, and specimens are rare. 

 Two of the species are represented in Figs. 316 B, C. 



Fig. 316 B is the Buthotrephis gracilis H., and Fig. 316 C, B. succulosus H. The figures 

 represent only portions of these plants. 



Fig. 316 B. 



Fig. 316 C. 



Fig. 316 B, Buthotrephis gracilis ; 316 C, B. succulo.-us 



2. Animals. 

 1. Trenton Epoch. 



The seas of the Trenton period were densely populated with animal 

 life. Many of the beds are made of the shells, corals, and crinoids, 

 packed down in bulk ; and most of the less fossiliferous compact kinds 

 have probably the same origin, and differ only in that the shells and 

 other relics were pulverized by the action "of the sea, and reduced to a 

 calcareous sand or mud before consolidation ; while others may be of 

 Rhizopod origin. 



The same four sub-kingdoms of invertebrate animal life were repre- 

 sented as in the preceding period, and only by marine species. All 

 the grander subdivisions of the Radiate as well as the Molluscan sub- 

 kingdom had their species. The Articulates were still confined to the 

 inferior aquatic classes of Worms and Crustaceans. 



